title: Three-dimensional model of Salmonella's needle complex at subnanometer resolution.
abstract: Type III secretion systems (T3SSs) are essential virulence factors used by many Gram-negative bacteria to inject proteins that make eukaryotic host cells accessible to invasion. The T3SS core structure, the needle complex (NC), is a ~3.5 megadalton-sized, oligomeric, membrane-embedded complex. Analyzing cryo-electron microscopy images of top views of NCs or NC substructures from Salmonella typhimurium revealed a 24-fold symmetry for the inner rings and a 15-fold symmetry for the outer rings, giving an overall C3 symmetry. Local refinement and averaging showed the organization of the central core and allowed us to reconstruct a subnanometer composite structure of the NC, which together with confident docking of atomic structures reveal insights into its overall organization and structural requirements during assembly.
authors.affiliation: Research Institute of Molecular Pathology, Dr. Bohr Gasse 7, A-1030 Vienna, Austria.
authors.forename: Oliver
authors.initials: O
authors.lastname: Schraidt
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Marlovits
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000648:ultrastructure; D058947:Bacterial Secretion Systems; D020285:Cryoelectron Microscopy; D018360:Crystallography, X-Ray; D007091:Image Processing, Computer-Assisted; D008565:Membrane Proteins / Q000737:chemistry* / Q000648:ultrastructure; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000648:ultrastructure; D008958:Models, Molecular; D009154:Mutation; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012486:Salmonella typhimurium / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; D058947:Bacterial Secretion Systems; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C079790:PrgH protein, Salmonella typhimurium; C556739:PrgK protein, Salmonella typhimurium; C090991:invG protein, Salmonella typhimurium